You watched a Sco video that applies to literally sub 0.1% of the player base?
Basically this. The tanks are balanced close enough together so that they can all do just about any content. Demon Hunters can tank Mythic raids just fine.
Now, if you are tanking Mythic Raids the first week they are out, and are therefore pretty undergeared for the content, some cracks start to show. World first guilds pick the tanks (and their whole comp really) based on what performs best under that extreme level of pressure, and BM's ability to smooth out damage is going to be better than Vengeance's or Blood's self healing. If you are learning the fights and gearing up at a more normal pace, you'll be just fine with anything, and you'll be better served learning your class better than rerolling.
TLDR:
Que tienes que ir overgeared (raid que se centra en equiparse bien) o para progresion de raid normal/media vas a pasarlo mal como DH tank.
